Uses object as base for local config definition [nodejs] (#159)

Fixes #158

Author: isaikevych

packages/opencensus-nodejs/src/trace/tracing.ts

@@ -32,7 +32,7 @@ export class Tracing implements core.Tracing {
   /** Plugin names */
   private defaultPlugins: core.PluginNames;
   /** A configuration object to start the tracing */
-  private configLocal: core.Config = null;
+  private configLocal: core.Config = {};
   /** An object to log information to */
   private logger: core.Logger = null;
   /** Singleton instance */
@@ -94,31 +94,29 @@ export class Tracing implements core.Tracing {
     this.activeLocal = false;
     this.tracer.stop();
     this.pluginLoader.unloadPlugins();
-    this.configLocal = null;
+    this.configLocal = {};
     this.logger = null;
   }
 
 
   /** Gets the exporter. */
   get exporter(): core.Exporter {
-    return this.configLocal ? this.configLocal.exporter as core.Exporter : null;
+    return this.configLocal.exporter ?
+        this.configLocal.exporter as core.Exporter :
+        null;
   }
 
   /**
    * Registers an exporter to send the collected traces to.
    * @param exporter The exporter to send the traces to.
    */
   registerExporter(exporter: core.Exporter): core.Tracing {
+    if (this.configLocal.exporter) {
+      this.unregisterExporter(this.configLocal.exporter);
+    }
     if (exporter) {
-      if (this.configLocal.exporter) {
-        this.unregisterExporter(this.configLocal.exporter);
-      }
       this.configLocal.exporter = exporter;
       this.tracer.registerSpanEventListener(exporter);
-    } else {
-      if (this.configLocal.exporter) {
-        this.unregisterExporter(this.configLocal.exporter);
-      }
     }
     return this;
   }

packages/opencensus-nodejs/test/test-tracing.ts

@@ -168,10 +168,9 @@ describe('Tracing', () => {
       assert.ok(tracing.config);
       assert.ok(tracing.tracer.active);
       tracing.stop();
-      assert.ok(!tracing.config);
       assert.ok(!tracing.tracer.active);
       assert.strictEqual(tracing.exporter, null);
-      assert.strictEqual(tracing.config, null);
+      assert.deepEqual(tracing.config, {});
     });
   });